GUIDELINES FOR MARINE LIFTING & LOWERING OPERATIONS 0027/ND Rev 11 Page 64 of 84 18.2 SAFETY 18.2.1
See Section 5 of 0001/ND, Ref. [1] for information on Health, Safety and Environment.
18.3 WEATHER-RESTRICTED OPERATIONS AND WEATHER FORECASTS 18.3.1
Section 7.3 of 0001/ND, Ref. [1], “General Guidelines for Marine Projects” applies for all weather-
restricted operations.
18.3.2
Section 7.3.6 of 0001/ND, Ref. [1], “General Guidelines for Marine Projects” applies to weather
forecasts.
18.3.3
In field monitoring of waves (height, direction and period) should be considered to enhance the
forecasts for each specific lift operation where a Certificate of Approval is required.
18.3.4
In field monitoring of currents (speed and direction) for subsea lifts in areas where it is known that high
currents exist in the water column should be considered to enhance the forecasts where a Certificate
of Approval is required.
18.4 ENVIRONMENTAL DESIGN CRITERIA 18.4.1
Section 7 of 0001/ND, Ref. [1], “General Guidelines for Marine Projects” applies to metocean criteria.
18.4.2
Seasonal current speeds with water depth variations (part from in shallow water), wave and wind data
shall be provided for the field location, in the form of monthly or seasonal scatter diagrams.
18.4.3
Operational criteria such as wind speed, wave conditions, relative motions etc. should be established
in the design phase. The design conditions for installation shall be agreed with GL Noble Denton at as
early a stage as possible.
18.5 SURVEY AND POSITIONING 18.5.1
A geophysical and geotechnical survey of sufficient resolution shall be carried out during the detailed
design phase to determine the nature and the bathymetry of the seabed. This is to include soil
characteristics and stability if required.
18.5.2
Comprehensive pre-installation site survey reports shall be issued (local structures, seabed
bathymetry, obstacles, pipelines etc.).
18.5.3
Surface positioning for installation shall be achieved using a calibrated GPS or DGPS system. There
shall be back-up reference systems available in the event that the primary reference system fails.
18.5.4
If a structure has to be positioned subsea in a location where there is no seabed infrastructure, a pre-
calibrated LBL or USBL arraymay be required. Transponders shall be deployed and surveyed in / on
the installed structure so that it interfaces with the array in terms of position and heading. Survey /
structure acoustic systems shall be designed and documented such that conflicts with DP References,
ROV transponders and divers are avoided.
